The present disclosure is directed to electrospraying devices and processes. In particular, the present disclosure is directed to electrospraying devices and processes for generating coagulation-based neutralized droplets and resulting nanoparticles.
Electrospraying involves applying a high electrical potential to a liquid-filled needle, which results in the formation of a liquid cone at the tip of the needle. A fine liquid jet emerges from the tip of the liquid cone and breaks up into fine droplets. Electrosprayed droplets are typically highly charged and unstable. Some of the applications require neutralization of the electrosprayed droplets. Original attempts to neutralize the droplets were based on ion producing means, including radioactive materials, corona discharge source and photon ionization source.
For example, as shown in FIG. 1, a conventional electrospray device 10 includes needle 12 supplied with a liquid 14 that flows in the direction of arrow 16. An electrical potential 18 is applied to liquid 14, which forms liquid cone 20 at the tip of needle 12. A liquid jet 22 emerges from the tip of liquid cone 20 and breaks up into fine droplets. The droplets carry a high electric charge of the same polarity as the electric potential (i.e. the droplets are positively charged if electric potential 18 is positive, and vice versa). Since the droplets have the same polarity of charge, they repel each other and spread out to form spray 24, which moves toward an electrically ground surface 26. As the liquid evaporates, these droplets often shed off finer droplets to remain stable. As such, electrospray is a useful device for many applications.
However, a number of important applications require neutralization of the droplets, so they are stabilized. One technique for neutralizing the droplets involves an ionization-based neutralization process. However, this process has an efficiency of about 10% and results in a host of problems, such as radiation safety and ozone generation. An alternative technique to overcome these problems involves a coagulation-based neutralization, which involved two oppositely charged electrosprays, created by opposite electrical potentials.